Lately, I have noticed that the Crippling Grasp buff tracker disappears instantly if it has been weapon swap/block canceled. It's messing my whole rotation up because I can't see when Crip Grasp is about to run out and what not

Others have reported this and it is not actually a bug nor doing what it seems to be doing. I will attempt to explain.

The game no longer classifies the buffs applied by abilities like Crippling Grasp by the name of the ability. Instead, the game itself now registers these buffs according to the effect they apply, Major Expedition in the case of Crippling Grasp. This is the name the game itself gives it. You can verify this by opening your stat sheet and looking at your buffs there which the game creates. You will see Major Expedition NOT Crippling Grasp.

What you are seeing appear and disappear isn't the buff on you but the DEBUFF on the target, and it likely isn't just randomly disapearing, but instead goes away when your cursor moves off a target with the debuff, or you go into mouse cursor mode.

Also, if you are attempting to track Crippling Grasp by assigning it by name to the Prominent Buffs bars it will not work since again, the game itself is not sending this name as what is actually being applied to you so there is nothing to track. Only the debuff on the target is tracked as "Crippling Grasp."

If you want to track your Crippling Grasp buff then you must look for Major Expedition and add that to the Prominent Buffs bar by name (or ID), not "Crippling Grasp."

I have considered creating a huge database correllating every ability in the game to the effects they apply and adding an option to change the name of those abilities to the source ability, but there are many problems:

It is a HUGE amount of work.

Many abilities add multiple effects (DK passive Major Prophecy / Major Savagery for one example)
which would result in duplicates of the same ability name in the buff trackers.

Performance would take a major hit having to parse this massive database every single time an ability was used/updated.

So, we are left with displaying buff information the way the game provides it to us.